Make ./tools/pull work when not on a branch
Make ./tools/pull work when not on a branch

When we are not currently on a branch, ./tools/pull will now fetch
origin, and verify and checkout origin/master.

boklm/tbb-testsuite,boklm/tbb-testsuite,boklm/tbb-testsuite,boklm/tbb-testsuite,boklm/tbb-testsuite